FILES argument behaving funny

FILES accepts an optional first argument, a string used to filter the output. The following formats are documented for this filter:

• projname/ lists the files in the given project
• // lists all projects (/ being [DEFAULT] and SYS/ being [SYS])
• TXT: or DAT: to list only files of that type in the current project

In most cases where the input would be invalid, it throws Illegal function call. However, if you pass a project name without the trailing slash, it still works. In addition, if you pass a path that doesn't exist...it fails silently. Nothing happens, no error. It does set RESULT to false though.

does it update ERRNUM or ERRLINE?